A generic upper strand trough for a generic trough pan is known from DE 102 22 598 A1. A wavy contour of the boundary line at the end edge of the trough bottom, on the one hand, and an associated wavy and preferably offset profile of the intermediate bottom, on the other hand, not only achieve a uniform run of the scrapers guided in the upper strand over the joint region, but at the same time ensure that sufficient angular movability is guaranteed even when two adjacent trough pans stand offset to one another by the amount of the maximum anglings permitted by trough pan connection means, such as, in particular, toggles.
When an exchangeable upper strand trough supported on an intermediate bottom has been in operational use for a lengthy period, sometimes considerable accumulations of fine coal appear in the gap at the joint between the trough plates of adjacent upper strand troughs, and this fine coal may be additionally compacted as a result of the movement of the scrapers and in adverse cases may even infiltrate between the trough bottom and intermediate bottom. In some rare cases, it has already been observed that the subsequent creep of fine coal in the joint gap between adjacent trough bottoms causes the upper strand troughs to be raised in relation to the intermediate bottom, with the result that the forces upon locking devices for the upper strand troughs increase considerably and, furthermore, it becomes considerably more difficult to release the upper strand trough for inspection or repair purposes. To mitigate this problem, it has already been proposed to provide fine coal passages in the intermediate bottom, so that fine coal, insofar as it accumulates between the trough bottom and intermediate bottom, can fall through the holes downward into the lower strand.